I have learnt from school that to electrolyse water we usually a little dilute sulphuric acid. Also, Na+, K+, NO3- and SO42- never preferentially discharges, so you can use chemicals like sodium sulfate, potassium nitrate or those containing only the above 4 ions.
Personally I think hydroxide is OK. Of course, safety must go first. I am not sure if nitrates of high concentration will decompose to give NO2 like concentrated nitric acid does.